McCain warned before the vote that “If there’s objection,
you are achieving the objectives of Vladimir Putin...and I do not
say that lightly.”

Paul then entered the Senate chamber, voted against the
accession protocol, and exited.

“The only conclusion you can draw when he walks away is he has no
argument to be made,” McCain said after Paul walked out abruptly,
according to
The Washington Examiner. "The senator from Kentucky is now
working for Vladimir Putin."

Russian President Vladimir Putin is staunchly opposed to
Montengro's accession to NATO, which he views as a threat to
Russian sovereignty. Albania and Croatia joined the
alliance 2009.

"Senator McCain believes that the person who benefits the most
from Congress’s failure to ratify Montenegro’s ascension to NATO
is Vladimir Putin, whose government has sought to destroy the
NATO alliance, erode confidence in America’s commitments to its
allies, overthrow the duly-elected government of Montenegro, and
undermine democratic institutions throughout Europe," McCain's
spokesperson, Julie Tarallo, told Business Insider on Wednesday.

"The overwhelming majority of senators who support this
treaty, and certainly the people of Montenegro, deserved an
explanation from Senator Paul on the Senate floor as to why he
sought to prevent this small, brave country from joining in the
defense of the free world," Tarallo added.

For Montenegro to move forward with the accession process,
which was approved in May, the treaty has to be ratified by the
US Senate by unanimous
consent. Twenty-one of 28 NATO allies have
already backed Montenegro's accession.

Asked about McCain's comment, Paul stood by his decision to
block the treaty and said it would be "unwise to
expandthe monetary and military obligations of the
United States given the burden of our $20 trillion
debt."

"Currently, the United States has troops in dozens of
countries and is actively fighting in Iraq, Syria, Libya, and
Yemen (with the occasional drone strike in Pakistan)," Paul told
Business Insider in a statement provided by his
office. "In addition, the United States is pledged to defend
28 countries in NATO."

McCain promised Montenegro Prime Minister Dusko
Markovic in January that the Senate would ratify the treaty
soon, according to
Radio Free Europe.

Markovic was the target of a coup plot, allegedly
orchestrated by Russian intelligence agents, to overthrow
Montenegro's pro-NATO government and replace it with a
Russia-friendly regime,
The New York Times reported. The plot was uncovered in
November after the pro-Russian mercenary who helped organize it
was arrested by Montenegrin police.